Simulation of a metal nano-strip grating distributed Bragg reflector (DBR) Laser

Abstract

The edge-emitting distributed Bragg reflector (DBR) laser with a metal nano-strip grating is proposed. It achieves a high reflectivity with a much shorter grating length of 200μm due to the high refractive index contrast of the metal and the semiconductor. Moreover, the modal coupling (κL) of the grating can be tuned in a wide range by simply changing the design parameters of the metal nano-structure. In this work, the metal grating is investigated by the coupled-wave theory (CWT) and the complex mode matching method (CMMM). Results from these two methods are compared and the effects of changing the grating parameters, such as the spacing of the grating and the core region, the thickness of nano-strips and the duty cycle, are discussed regarding the peak reflectivity and the full-width half-maximum (FWHM) of the reflection spectrum. Further simulation of the laser output with the multi-mode rate equation model demonstrates the single-mode operation for a broad range of the metal grating’s design parameters, thus the design freedom is provided. For various applications of the DBR laser, the requirements such as a shorter cavity length, a lower threshold current, or a very high SMSR can be satisfied by properly setting the design parameters.